Social context affects the motivation of laboratory mice, Mus musculus, to gain access to resources

Consumer demand studies measuring the motivation that animals have for resources have almost exclusively used gregarious species, but have tested animals housed in isolation. The motivation that gregarious animals have for resources could be increased or decreased by the presence or absence of companion animals, that is, the social context. I trained a single mouse from each of six groups to perform an operant task that was quantifiable and would not be performed fortuitously or learnt by nontrained mice. The trained mice were housed with nontrained cagemates in a start cage that required them to perform the operant task to enter a resource cage providing either additional space or a running wheel. The presence of cagemates in the start cage significantly decreased the number of visits/24 h to the running wheel, the number of bouts and the duration of wheel running, but had no effect on the number of visits to additional space. The presence of cagemates increased the time spent in the resource cage whether this provided additional space or a running wheel, indicating that the mice overcompensated for the reduced frequency of visits. These results show that social context can have a significant effect on the motivation that animals have for resources, and that this effect is resource dependent. The influence of social context should therefore be considered in the design and interpretation of consumer demand studies. Copyright 2003 Published by Elsevier Ltd on behalf of The Association for the Study of Animal Behaviour.